The present invention relates to data structures which include first data (which, e.g., may be referred to as message or payload data) that is coded and decoded using a clock period. According to embodiments of the invention, such a data structure also includes second data from which can be extracted the clock period used to code the first data in the data structure and with which the first data in the data structure can be decoded. Such data structures may be used in various data transfer and data communication applications, e.g., to transfer data between a computer terminal and a user device in connection with authentication of the user.
The data structures described herein may be used, e.g., as a coded light signal emitted by a computer terminal to a user device, e.g., as described in U.S. application Ser. No. 10/651,361, filed on Aug. 29, 2003, which is assigned to the assignee of this application. The disclosure of U.S. application Ser. No. 10/651,361 is incorporated herein by reference.